Abstract: The object of the present invention is to offer an sound reproduction apparatus equipped with a speaker having a drastically improved acoustic characteristics securing a stable and high S/N ratio over a wide frequency range. In order to accomplish these objects, the inputted audio signal is amplified by a power amplifier and is reproduced in an acoustic output by driving a speaker, and the reproduced acoustic output is detected by a microphone disposed in a closed cabinet together with said speaker and the detected signal is amplified by a microphone amplifier and is processed by a filter. Then, the output signal from said filter and the input signal to said power amplifier are added and processed, and the difference signal between the added signal and said inputted audio signal is used as an input signal to said power amplifier constituting a negative feedback circuit accomplishing the objects of this invention.

Abstract: A method of mass-producing IC devices includes the steps of: forming a plurality of types of conductor patterns on a ribbonlike insulating substrate, separating the ribbonlike substrate to form a plurality of types of divided substrates, causing at least one of the conductor patterns of the same type to be included in each of the divided substrates, and sending the divided substrates including the conductor patterns of the same type to the same dedicated assembling line.